Desenvolvimento de um sistema híbrido nanoestruturado de Laponita® e Papaína

Abstract

Papain (PAP) is an enzyme that has several pharmacological activities such as healing, antimicrobial and anti-inflammatory properties. However, it has low stability, which is a problem for the development of therapeutic formulations. In view of this, a strategy to overcome this adversity is to perform immobilization through the PAP adsorption technique on substrates, for example, laponite® (LAP). Thus, the objective of this work was to develop and characterize a nanostructured hybrid system (SHN) composed of LAP and PAP. For this, the experimental conditions of adsorption of this enzyme in LAP were evaluated, considering the effect of pH, initial concentration of PAP and contact time. Equilibrium and kinetic studies were carried out within the range of pH 5.0 to 7.0, with reaction times from 0 to 2880 min and with concentrations from 4.500 to 25.500 mg/L in sodium phosphate buffer, under stirring at 200 rpm. Langmuir, Freundlich and Temkin isothermal models were used, as well as pseudo-first order, pseudo-second order and Elovich kinetics. The SHN were characterized by Fourier transform infrared spectroscopy (FTIR), thermogravimetric and derivative analysis (TG and DTG), differential thermal analysis (DTA) and X-ray diffraction (XRD). The results showed that the interaction between PAP-LAP is influenced by pH, with maximum adsorption at pH 7, the isotherm study showed that the equilibrium conditions of PAP-LAP adsorption obey the Freundlich model. Adsorption kinetics showed a fast phase up to 60 min and a slow one from 120 to 2880 min, fitting the pseudo-second order model. The maximum amount of PAP adsorbed on the LAP was 1243.6 mg/g, obtained at a concentration of 15.500 mg/L, at pH 7, in a time of 2880 min. The intercalation of PAP in the LAP was verified by the FTIR and XRD patterns, since an increase in the interlamellar distance from 1.252 nm (LAP) to 1.315 nm (SHN) was seen, with SHN spectra showing smaller vibrations referring to the PAP in the LAP, when compared to the isolated spectra of the drug. The mass loss profile in relation to time, demonstrated from the results obtained from TG/DTG/DTA, highlighted that the greatest losses occurred at pH 7 and at the highest concentration of drug, which was the work standard chosen. Considering the results obtained, it can be concluded that the process of adsorption of PAP in LAP promotes the feasibility of obtaining a SHN, with the ability to overcome the low enzymatic stability. It was proved that the increase in the concentration of PAP and the pH of the medium caused an increase in adsorption, at pH 7 there is formation of a heterogeneous surface and the adsorption occurs in multilayer, which is related to the intercalation capacity of PAP in the LAP lamellae. It is possible to point out that the longer the contact time between the adsorbate and the adsorbent, the greater the adsorption capacity due to the exfoliation of the lamellae of this clay mineral, this process represents a viable alternative to remedy the industrial need for PAP immobilization.